好程式員Java學習路線分享mybatis映射
好程式員Java學習路線分享mybatis映射,希望對大家有所幫助。
Mybatis 1對1關聯 實作方式
- 通過resultType方式
- 通過級聯屬性的方式【resultType 和 resultMap方式】
- 通過association關聯的方式
- 通過association的分步查詢方式
- 通過包裝類的雙association的關聯方式
- 通過association的嵌套定義方式
案例: 查詢 訂單 對應的使用者資訊
Sql建表語句
使用者表:
-- ---------------------------- -- Table structure for `user` -- ---------------------------- DROP TABLE IF EXISTS `user`; CREATE TABLE `user` ( `id` int(11) NOT NULL AUTO_INCREMENT, `username` varchar(32) NOT NULL COMMENT '使用者名稱', `birthday` date DEFAULT NULL COMMENT '生日', `sex` char(1) DEFAULT NULL COMMENT '性别', `address` varchar(256) DEFAULT NULL COMMENT '位址', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=27 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of user -- ---------------------------- INSERT INTO `user` VALUES ('1', '王五', '2019-08-30', '2', '杭州'); INSERT INTO `user` VALUES ('10', '張三', '2014-07-10', '1', '北京市'); INSERT INTO `user` VALUES ('16', '張小明', '2019-08-15', '1', '河南鄭州'); INSERT INTO `user` VALUES ('22', '陳小明', '2019-08-08', '1', '河南鄭州'); INSERT INTO `user` VALUES ('24', '張三豐', '2019-08-15', '1', '長沙'); INSERT INTO `user` VALUES ('25', '吳小明', '2019-08-08', '1', '河南鄭州'); INSERT INTO `user` VALUES ('26', '王五', '2019-08-14', '2', '武漢'); |
訂單表:
-- ---------------------------- -- Table structure for `orders` -- ---------------------------- DROP TABLE IF EXISTS `orders`; CREATE TABLE `orders` ( `id` int(11) NOT NULL AUTO_INCREMENT, `user_id` int(11) NOT NULL COMMENT '下單使用者id', `number` varchar(32) NOT NULL COMMENT '訂單号', `createtime` datetime NOT NULL COMMENT '建立訂單時間', `note` varchar(100) DEFAULT NULL COMMENT '備注', PRIMARY KEY (`id`), KEY `FK_orders_1` (`user_id`), CONSTRAINT `FK_orders_id` FOREIGN KEY (`user_id`) REFERENCES `user` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION ) ENGINE=InnoDB AUTO_INCREMENT=8 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of orders -- ---------------------------- INSERT INTO `orders` VALUES ('3', '1', '1000010', '2015-02-04 13:22:35', null); INSERT INTO `orders` VALUES ('4', '1', '1000011', '2015-02-03 13:22:41', null); INSERT INTO `orders` VALUES ('5', '10', '1000012', '2015-02-12 16:13:23', null); INSERT INTO `orders` VALUES ('6', '10', '1000013', '2015-08-30 10:11:56', null); INSERT INTO `orders` VALUES ('7', '16', '100014', '2019-08-16 10:12:54', null); |
實體類:
使用者:User
public class User { private Integer id; private String name; private Date birthday; private String sex; private String address; //getter.. setter.. toString.. } |
訂單:Orders
public class Orders { private Integer id; private Integer userId; private String number; private Date createtime; private String note; //getter.. setter.. toString.. } |
方式一:resultType方式
一個訂單 對應 一個使用者
對訂單實體類進行擴充: 【隻增加 對應的字段 ;例如案例中的 使用者名稱】
建立OrdersExtByColumn 的擴充類,繼承 Orders, 并增加相應的字段
public class OrdersExtByColumn extends Orders { private String username; //getter.. setter.. toString.. } |
OrdersMapper映射檔案中,寫對應的sql語句
<select id="queryOrdersByType" parameterType="int" resultType="OrdersExtByColumn"> SELECT o.id,number,createtime,note,user_id userId,username FROM orders o ,user u WHERE o.id = u.id and o.id = #{id} </select> |
編寫測試程式:
public class TestAssociation { private SqlSession sqlSession; @Before public void initSqlSession(){ //1.讀取核心配置檔案 SqlMapConfig.xml InputStream resourceAsStream = TestMain.class.getClassLoader().getResourceAsStream("SqlMapConfig.xml"); //2. 産生 SqlSessionFactory SqlSessionFactory sqlSessionFactory = new SqlSessionFactoryBuilder().build(resourceAsStream); //3. 産生 SqlSession sqlSession = sqlSessionFactory.openSession(); } @Test public void testQryName(){ //找對應的sqlID String sqlID = "orders.queryOrdersByType"; //sqlSession 執行對應的資料庫操作 OrdersExtByColumn orderInfo = sqlSession.selectOne(sqlID, 3); //對查詢的結果進行處理 System.out.println(orderInfo); } @After public void closeResource(){ sqlSession.close(); } } |
方式二 : 級聯屬性的方式
在orders類中, 增加 級聯屬性User user;
![](https://img.laitimes.com/img/9ZDMuAjOiMmIsIjOiQnIsIyZuBHL0FWby9mZvwVZnFWbp1zczV2YvJHctM3cv1Ce-4WNHNWdjRUT0sGROFTW650MwM0T5FkeOFza610MFR1T3tGRNVTRE1UewknT10kaOJTWU1kdrRUT1UERNlHO55UNNpmTykFVNZ3YyI2cKJDT0ljMZVXTzold41WW15UbMRTRE1UejdlYwlTeMZTTINGMShUYvwlbj5yZtlmbkN3YuQnclZnbvN2Ztl2Lc9CX6MHc0RHaiojIsJye.jpg)
ResultType方式:
ResultMap方式:
方式三:association關聯的方式
方式四:association的分步查詢方式
分步查詢:即多個sql查詢 算出結果
此種方式,可以結合mybatis核心配置檔案mybatisCfg.xml的配置項,産生延遲緩存;
mybatisCfg.xml 延遲加載相關設定項
方式五:包裝類的雙association的關聯方式
建立包裝類:
OrdersAndUser
public class OrdersAndUser { private Orders orders; private User user ; //getter.. setter.. } |
方式六:内嵌association級聯
這種内嵌association會關聯三張表;
需求簡單變更為: 從某訂單詳情中,查詢訂單及對應 使用者資訊
追加一張訂單詳情表
-- ---------------------------- -- Table structure for `orderdetail` -- ---------------------------- DROP TABLE IF EXISTS `orderdetail`; CREATE TABLE `orderdetail` ( `id` int(11) NOT NULL AUTO_INCREMENT, `orders_id` int(11) NOT NULL COMMENT '訂單id', `items_id` int(11) NOT NULL COMMENT '商品id', `items_num` int(11) DEFAULT NULL COMMENT '商品購買數量', PRIMARY KEY (`id`), KEY `FK_orderdetail_1` (`orders_id`), KEY `FK_orderdetail_2` (`items_id`), CONSTRAINT `FK_orderdetail_1` FOREIGN KEY (`orders_id`) REFERENCES `orders` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION, CONSTRAINT `FK_orderdetail_2` FOREIGN KEY (`items_id`) REFERENCES `items` (`id`) ON DELETE NO ACTION ON UPDATE NO ACTION ) ENGINE=InnoDB AUTO_INCREMENT=5 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of orderdetail -- ---------------------------- INSERT INTO `orderdetail` VALUES ('1', '3', '1', '1'); INSERT INTO `orderdetail` VALUES ('2', '3', '2', '3'); INSERT INTO `orderdetail` VALUES ('3', '4', '3', '4'); INSERT INTO `orderdetail` VALUES ('4', '4', '2', '3'); |
新增OrderDeatil類 【關聯Orders屬性】
public class OrderDetail { private Integer id; private Integer orderId; private Integer itemsId; private Integer itemsNum; private Orders orders; //setter.. getter.. } |